1,3-butadiene is a representative raw material of synthetic rubbers and is one of major basic oils, the price of which sharply changes according to supply and demand situation in petrochemistry. Naphtha cracking, direct dehydrogenation of normal-butene, oxidative dehydrogenation of normal-butene and the like are used for preparation of 1,3-butadiene. Naphtha cracking for preparing 1,3-butadiene has an advantage of high price competitiveness as compared to other methods, but disadvantageously has difficulty in increasing production of only butadiene and requires large-scale investment for this purpose, because naphtha cracking is not a process for preparing only butadiene and thus relates to demand for ethylene and propylene. Advantageously, oxidative dehydrogenation of normal-butene is performed at a low temperature and reduces energy consumption because it is an exothermic reaction, unlike direct dehydrogenation, and inhibits production of carbon precipitates which poisons catalysts and thereby reduces lifespan of the catalysts, or removes the produced carbon precipitates due to addition of an oxidizing agent. Various types of metal oxides as the catalysts are used for oxidative dehydrogenation of normal-butene. In particular, bismuth-molybdate-based catalysts are known to exhibit superior catalyst activity. To increase pure bismuth-molybdate catalysts composed of only bismuth molybdenum oxide and activity thereof, multi-component bismuth-molybdate catalysts to which various metal components are added are actively researched. For example, U.S. Pat. No. 6,921,831 discloses various examples of Qd[BiaPbbMocOy]eOx (Q=Cu, Au, V or a mixture thereof) catalysts, U.S. Pat. No. 8,003,840 which discloses a bismuth-molybdate catalyst containing an a phase and an γ phase which are mixed each other, and U.S. Pat. No. 8,367,885 discloses a Mo—Bi—Fe—Ni multi-component catalyst using these catalysts which has an n-butene conversion ratio of about 55 to about 65% and 1,3-butadiene yield of about 60% or less.
Co-precipitation is generally used in the preparation of the multi-component metal oxide catalyst such as bismuth-molybdate catalyst. The co-precipitation is a method of preparing catalysts by mixing two or more metal solutions under control of pH and inducing precipitation, which enables production of a powder with a high purity at a low cost due to simple process and is industrially inconvenient. However, pH and concentrations are changed as co-precipitation proceeds, thus making it difficult to obtain a powder having uniform and fine particles. In addition, a high baking temperature is required to form a crystal phase of the composite oxide catalyst, thus disadvantageously reducing the surface area of catalyst acting according to the mechanism of adsorption-reaction-desorption. Composite oxide catalysts formed of only metal oxide prepared by co-precipitation are known to generally have a surface area of 10 m2/g.
EP Patent No. 2,343,123 discloses multi-component bismuth-molybdate containing at least cobalt or nickel, in which particles of silica such as fumed silica are dispersed, in order to improve surface area.
However, there is a demand for continued research associated with composite oxide catalysts with a high surface area which improves conversion ratio of butene, as well as selectivity and yield of 1,3-butadiene and enhances economic efficiency.